The present invention relates to photographic printing systems. In particular, the present inventnion is a film measurement system which measures the optical characteristics of the photographic film prior to printing.
Photographic printers produce color or black and white prints or transparencies from photographic film originals (generally negatives). High intensity light is passed through the film and imaged on the photosensitive print medium (film or paper). The photographic emulsion layer on the print paper pr film is exposed and subsequently processed to produce a print or transparency of the scene contained in the original.
Automatic photographic printers often include automatic density correction (ADC) or color or density scanning systems which provide measurements of the transmission density of the negative at defined discrete or continuous areas, as opposed to an average or integrated measurement over the entire negative. The measurements of the negative so derived can be used as a sole means of exposure determination, or in conjunction with other measurements to calculate the proper exposure. Examples of these mechanisms are described in the following U.S. Pat. Nos.: Stimson 3,232,192; Wick et al 3,345,309; Bowker et al 3,519,347; Wick et al 3,523,728; Harvey 3,669,553; Rickard et al 3,690,765; Huboi et al 3,694,074; Zahn et al 3,709,613; Paulous 3,724,947; Huboi et al 3,790,275; Zahn et al 3,813,158; Crete et al 3,873,200; Amano et al 3,888,580; Dailey 3,944,362; Pone, Jr. et al 4,017,179.
Some of the systems described in these patents use moving optical elements or a cathode ray tube to provide the desired scanning, while other systems have used one or more sensors in conjunction with optical prisms or fibers to view different portions of the negative. In general, a system without moving optical elements is desirable from a cost, size and reliability standpoint.
One problem which all of these systems encounter is the different film sizes which may be printed by the photographic printer. The standard film sizes (110, 126, and 135) differ significantly in size. The 110 size film presents a particular problem because of its extremely small size.
Some of the prior art systems have simply used the same optical system for all film sizes. As a result, the larger size films (126 and 135) yield far more data points at a proportionately smaller measurement spot size to frame size than does 110 size film, thereby requiring excess data manipulation or multiple algorithms to handle the data. Alternatively, some systems have used completely different optical and sensor systems for each film size. This is objectionable from a cost standpoint and from a user standpoint due to the complicated changes which must be made each time a different size film is to be printed.